This invention relates to new and useful improvements in orthodontics, and in particular, the portion of orthodontics relating to the generation of differential distal movement of teeth.
Conventionally, extra-oral anchorage is used for the movement of teeth in which opposite and equal forces are applied between the relatively immovable cranium and/or neck and the tooth or teeth concerned, and difficulty has been experienced particularly with the use of unilateral or asymmetric headgear with which the clinician attempts to exert a greater distalization force upon the tooth or teeth on one side than the other.
The use of asymmetric headgear for differential distalization, in most cases, produces clinically undesirable side effects due primarily to the unwanted lateral forces that are applied to the molar as will hereinafter be described.
Attempts have been made in the past to overcome these disadvantages, one of which is the use of a combination inner arch and outer bow secured together with the outer bow being positioned asymmetrically to the side that requires excess distalization. However, analysis of the forces involved show that the undesirable lateral movement is still present.